Device for squeezing flowable material out of a tubular bag

ABSTRACT

The inventive device for squeezing out flowable material includes an elongate tubular bag ( 1 ) containing the material, as well as an ejection device ( 2, 5 ) which has a cylindrical chamber ( 10 ) with a plunger ( 5 ) located therein and an outflow opening ( 9 ) to insert the bag therein. The bag has an opening ( 8 ) at one end surrounded by the bag ( 1 ) shoulder ( 12 ) and the sealing washer ( 13 ). For improved sealing, the sealing member ( 15, 17, 19, 22, 25 ) engages the chamber fore-part ( 11 ) surrounding the outflow opening ( 9 ). Additional parts may be provided to maintain said sealing member on the fore-part.

CROSS-REFERENCE TO RELATED APPLICATION

This is the national stage of International Application No.PCT/EP97/04337 filed Aug. 8, 1997.

BACKGROUND OF THE INVENTION

It is known to squeeze a flowable, pasty mass such as sealing mass ordental impression mass out of a tubular bag in that the latter isintroduced into a cylindrical space which is acted upon from one end bya plunger and has a discharge opening or ejection nozzle at the otherend, at which the bag has been opened. In this case, particular value isplaced upon the sealing of that end of the tubular bag which containsthe bag opening in relation to that end of the cylindrical space whichforms the discharge opening and the ejection nozzle. If, for thispurpose, the tubular bag is fixedly connected to the unit forming thecylindrical space (FR-A 1 161 905), the multiple use of thesqueezing-out unit for a plurality of tubular bags is made impossible.To avoid this disadvantage, an arrangement for squeezing out fromexchangeable tubular bags has become known (EP-A 541 972), in whicharrangement the gathered end of the tubular bag, which end forms the bagopening, is fixedly connected to a sealing ring which has a conicalsealing surface which cooperates with a corresponding conical sealingsurface in the discharge opening of the squeezing-out unit. Under theaction of the squeezing-out plunger, the cone of the sealing ring ispressed into the conical discharge opening, provided that it has beenadequately centred in advance. If the centring is inadequate, no sealingtakes place. If the cone of the sealing ring sits precisely centrally inthe discharge opening, it appears to be possible to achieve an adequatesealing action as long as the action of the plunger force persists.However, this sealing action ends when, upon termination of the plungerforce, the arrangement “breathes”. Since, during squeezing out, thegreatest part of the pressure drop does not occur in the bag opening orthe discharge opening of the squeezing-out unit, but in the downstreamspaces of the nozzle and of the possibly present mixing device, aconsiderable pressure builds up, during squeezing out, in these spacesdownstream of the discharge opening, which pressures leads tocorresponding expansion of the associated wallings. When thesqueezing-out force of the plunger ends, this expansion then leads to aback pressure and a back flow of the mass in the region of the dischargeopening. As a result of this, the cone of the sealing ring may be liftedoff from its conical seat in the discharge opening; the sealed gap opensand the mass can penetrate into the space to be sealed off betweensealing ring and tubular bag on the one hand and cylindrical space onthe other hand. Furthermore, the mutual centering may be lost, so thatthe cone of the sealing ring is not passed back into the correct seatupon the next application of pressure. Accordingly, contamination of theunit cannot be entirely avoided by the known arrangement. In addition,there is the disadvantage that in the case of the exchange of thetubular bag the discharge opening must be carefully cleaned, becauseotherwise residues of the mass which have remained there and possiblysolidified make a complete sealing off impossible, even during theaction of the squeezing-out force; this then leads to furthercontamination of the unit. Furthermore, the known mode of sealing offrequires careful production and assembly of the parts participating inthe sealing off; this being costly. In another known arrangement forsqueezing out from exchangeable tubular bags (FR-A 2 301 306, FIG. 4), aflat sealing ring is inserted between the flat end of the bag, which isprovided with a cross-shaped incision for forming a squeezing-outopening, and the end face of the cylinder space, surrounding thedischarge opening. This sealing ring is not connected to thy end of thebag. It has therefore been found that it cannot ensure a tight seal inthe region of folds in the bag.

SUMMARY OF THE INVENTION

The object of the invention is to provide an arrangement for squeezing afree-flowing substance out of an elongated tubular bag which is lessexpensive, permits an easy exchange of the tubular bag, and neverthelessensures adequate sealing.

The invention is based on the observation that leakage is often causedby the sealing ring being slightly oblique with respect to the axis ofthe bag, for example if the bag has been distorted as a result ofdeformation due to unskilled handling upon insertion into the cartridge.The invention avoids this effect by the sealing ring being connected tothe bag in an angularly movable fashion, so that it can align itselfwith the associated counter sealing surface. This angular mobility isbrought about by connecting the sealing ring to a disk or designing itas a disk which is adhesively bonded to the end face of the bag withinan annular bead facing the latter and of a diameter which issubstantially less than that of the bag. In this case, the disk regionoutside the annular bead remains free from the connection to the endface of the bag and can therefore move towards it on one side and awayfrom it on the other side, the annular bead forming a kind of tiltingbearing.

The capability of the sealing ring to align itself with the end facesurrounding the discharge opening produces a reliable sealing-offeffect. A cleaning of the end face cooperating with the sealingcomponents is frequently unnecessary, because experience shows that themass seldom advances to such an extent. Moreover, the cleaning of thissurface is easier than that of the discharge opening, because it is morereadily accessible and can be monitored more easily. The cooperatingsealing surfaces place less stringent requirements on precise productionand assembly, because it is not necessary to coordinate any diameterswhatsoever accurately with one another. Finally, the invention has theadvantage that the sealing off is independent of the respective designof the discharge opening and the tubular bags can accordingly be used indiffering squeezing-out units.

In general, the end face surrounding the discharge opening of thesqueezing-out unit is flat. In these circumstances, it is recommendedalso to design the sealing ring (possibly apart from projecting sealingcomponents) to be flat, so that it can extend parallel to the end face.This applies in particular in circumstances in which, according to afurther feature of the invention, it has an external diameter which isapproximately equal to, or only slightly smaller than, the diameter ofthe cylindrical space. The result of this is a good guiding andcentering of the end of the tubular bag upon introduction into theejection opening.

It is known to have the bag opening formed by a gathering of the bag,which gathering penetrates through the sealing ring and is cut away.According to the invention, this gathering lies freely in the dischargeopening. Thereby, it is achieved that, under the action of thesqueezing-out differential pressure, the gathering is applied to agreater or lesser extent to the walling of the discharge opening andthere forms a sealing off upstream of the sealing ring. Even where suchsealing off may not be complete, it does nevertheless obstruct thepassage of the mass, so that frequently the latter does not actuallyreach the sealing components of the sealing ring.

The sealing component or the sealing components of the sealing ring arepressed, by the squeezing-out force exerted by the plunger on thetubular bag, against the end face of the cylindrical space and are ablethereby to perform their sealing action during the squeezing-outprocess. They can be designed in various ways, in accordance with theknown principles of sealing technology. In the simplest case, thesubstantially flat surface of the sealing ring or the latter itselfforms the sealing component. However, it is also possible to provideparticular sealing components, projecting from its surface, in anydesired number. Expediently, they are designed in yielding fashion, sothat they can adapt in gap-free fashion to the counter sealing surfaceformed by the end face. The requirements imposed upon the accuracy ofproduction are thereby further curtailed. This applies to any form ofthe sealing component or of the sealing components, namely both in thecase of large area contact of the sealing ring designed in disk fashionwith the end face and also in circumstances in which the sealingcomponent is designed as annular projection. It may have, for example,the form of one or more circulating, thin sealing lips. The softness isthen given by the thinness of the sealing lip. In the case of anotherdesign, the sealing ring is provided with an additional, circulatingsoft material ring, for example a commercially available O-ring or aring of foam rubber having a closed surface. Such an additional annularpart can also be a part which is separate from the sealing ring andwhich abuts tightly thereagainst. This design has the advantage that thepart of the sealing ring which is designed together with the tubular bagas a throw-away part can be designed in a particularly low cost fashion,while the additional annular part, which has or forms the sealingcomponent, can be repeatedly used and can accordingly be formed in acorrespondingly more costly fashion.

In order to avoid the lifting off of the sealing components from the endface of the cylindrical space, according to a further feature of theinvention the sealing ring can be provided with a retaining partarresting it in the sealing position. The invention prefers twoembodiments of this concept.

In the case of the first embodiment of the retaining part, the disk isequipped with a suction holder holding it fast at the end face. This maycomprise one or more suction cups. Expediently, the sealing component isdesigned as a suction holder. This is the case in circumstances in whicha first, inner sealing ring and a second, outer sealing ring enclosewith the end face a space, the volume of which decreases as a result ofthe compression of the sealing rings against resilient deformation ofthe same, the compressed air between the sealing rings and the end faceis expelled and, upon cessation of the plunger force, cannot return intothe intermediate space without further ado, by reason of the sealingaction of the sealing rings. In this case, the sealing rings areexpediently designed as sealing lips, which point outwards from thesuction space, in order to facilitate the exit of the air from thesuction space, but to impede the re-entry of the air.

According to the second embodiment, a braking component is provided atthe end of the bag opposite the end of the bag containing the opening.This generally requires the bag to be pushed into the cylinder spacefrom the end remote from the discharge opening. The braking componentdisposed at the rear end of the tubular bag holds the bag firmly in therespective position in the cylindrical space. By means of friction, italso prevents a situation in which in the course of the removal andvertical erection of the cylinder with the outlet opening upwards, thebag slips backwards or even falls out of the cylinder. As a result ofthe fact that, upon insertion of the bag into the cylindrical space, thedrawing-in force is exerted directly on the braking component disposedat the rear end of the tubular bag, it does not need to be transferredvia the bag and its contents to the braking component, and accordinglyhas no effect on the internal pressure of the bag.

BRIEF DESCRIPTION OF THE DRAWINGS

In the text which follows, the invention is explained in greater detailwith reference to the drawing, which illustrates advantageousillustrative embodiments. In the drawing:

FIG. 1 shows an exemplary embodiment with a sealing ring fastened on thebag in an angularly movable fashion,

FIGS. 2 and 3 show an exemplary embodiment with a pair of lips designedas a suction holder and

FIG. 4 shows an exemplary embodiment with a braking disk arranged on therear end of the bag.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the tubular bag 1 within a so-called cartridge 2, whichcomprises a wall 3 and a floor 4. Its internal diameter is dimensionedin such a manner as to fit that of the tubular bag 1. Cartridges of thistype with tubular bags are used as exchangeable inserts in units for theexpulsion of plastic masses, for example in units for the expulsion ofdental multicomponent impression masses (EP-A 492 413). The cartridgesare inserted into the unit in such a way that a plunger specific to theunit can penetrate into the open end, remote from the floor, of thecartridge, in order to squeeze out the tubular bag 1. The end 7, whichis gathered together and which is closed in the storage condition, ofthe bag is cut away in such a way that a bag opening 8 is formed, whichopens into a discharge opening 9 set in the floor 4 of the cartridge. Asealing ring 13 is inserted between that end face 11 of the floor 4which faces the cylindrical space 10 of the cartridge and the shouldersurface 12 of the tubular bag 1. When the plunger compresses the tubularbag 1, the mass contained therein can flow through the bag opening 8 andthe discharge opening 9 into the downstream spaces of the unit, whichare not shown, in order for example to be mixed with another componentand finally to be applied in the desired manner. The pressure generatedby the plunger in the tubular bag 1 also acts, via the shoulder surface12, on the sealing ring 13, so that the latter forms an effectivesealing off between the end face 11 and the shoulder surface 12.Moreover, the gathering 7 is pressed against the wall surface of thedischarge opening 9, so that an upstream sealing is created at thisposition. The concept cylindrical space is not intended to state thatthe wall 3 has to be cylindrical; however, it is expediently so.

In the event of inattentive insertion of the deformed bag 1 into thecylinder 3, it may happen that the end face of the bag is slightlydistorted obliquely. The corresponding oblique position of the end faceis transferred to the sealing ring if the latter is designed as a diskor is connected to a disk which is adhesively bonded in full surfacefashion to the end face of the bag. Depending upon the design of theseal, the sealing action may suffer if the plane of the sealing ringdoes not stand precisely vertically to the cylinder axis. In order todeal with this risk, it is provided that the sealing ring 13 isconnected to the bag 1 in angularly movable fashion in relation to thebag axis 42. As a consequence of this, it can align itself in accordancewith its correct sealing position if it is pressed by the bag againstthe end face of the cartridge floor, even if the bag should be slightlydistorted.

FIG. 1 reveals that the disk 16 of the sealing ring, which is designatedas a whole by the reference numeral 13, is connected to the end face 12of the bag 1 by means of an adhesive bonding and sealing mass 40. Theconnection is restricted to the radially inner region of the disk 16 andthe end face 12 and is outwardly limited by a bead 41, which is providedin annular fashion on that end face of the disk 16 which faces the bag1, concentrically to the disk opening and to the disk periphery. Outsidethe annular bead 41, the disk 16 and the bag end face 12 are unconnectedand, as a rule, slightly lifted off from one another. The result of thisis that the disk 16 can tilt freely in relation to the bag end face 12within a certain angular range; in which case, the bead 41 is pressed onthe one side more and on the other side less into the bag. Any possibleoblique position of the bag, as is indicated in FIG. 2, is accordinglyunable to have an effect on the position of the disk 16 and the sealingaction of the O-ring 15.

In FIG. 1, it has been presupposed that the floor 4 of the cartridge isfixedly connected to its wall 3 and the tubular bag 1 is inserted intothe cartridge from that side which is remote from the expulsion side.However, it is also possible that the floor 4 can be released from thewall 3 in cover fashion for the insertion of the tubular bag 1. Themargin of the sealing ring 13 can be drawn up in a pot shape towards theside of the tubular bag 1, in order to enlarge the height (dimension inthe axial direction) of the peripheral surface, whereby a tilting overof the disk-shaped sealing ring upon introduction into the cartridge isavoided.

The sealing ring is designed as an annular disk 14, which, just like theend face 11, is designed to be flat. Its external diameter is notsubstantially smaller than that of the cylindrical space 10. Uponintroduction of the tubular bag into the cartridge, it can thereforeserve for the centering of the bag opening with respect to the dischargeopening. It consists of stiff plastic material, in order to be able toattend to this task. Expediently, it also has such great strength thatit can guarantee the position which is approximately flat or parallel tothe end face 11.

Close to the inner margin of the annular disk 14, an O-ring 15 (theremay also be a plurality) is tightly and preferably fixedly connected tothe annular disk 14, in that it is adhesively bonded into or clampedinto an annular groove, for example. It consists of soft rubber or foamrubber having a closed surface and accordingly abuts, under the pressureacting during the squeezing-out process, in gap-free fashion against theend face 11 and thus forms an effective protection against thepenetration of mass from the discharge opening 9, in the event that massshould pass through between the gathering 7 and the wall of thedischarge opening 9. In principle, the arrangement according to theinvention is exposed in just the same way as known arrangements, to the“breathing” of the device upon termination of the squeezing-outpressure. Since, however, the bag opening 8 can have a larger cleardiameter than known tubular bags, by reason of the absence of an annularpart penetrating into the discharge opening 9, its resistance to flow issmall, so that the extent of the “breathing” and thus the risk ofpenetration of mass between the gathering 8 of the tubular bag and thewall of the discharge opening 9 are smaller than in the case of knownarrangements.

The sealing component may assume different forms. It may, for example,be a layer of soft resilient material, for example foamed, resilientplastic material or rubber having an open or closed surface, cooperatingover a large surface area with the end face 11. It may also be formed byone or more annular projections or resilient sealing lips which aresharp in cross section and integral with the disk 16.

If the sealing component is formed by a soft layer, it may be fixedlyconnected to the annular disk 16, for example formed by a coatingprovided thereon or adhesively bonded to it. However, it can also be aseparate annular disk, which, if appropriate, can be used repeatedly.The sealing components can also be formed from a plurality of annularcirculating annular projections, which are sharp in cross section andwhich are integral with the annular disk and which abut against the endface 11. The material is chosen and the sharpness of the annularprojections is dimensioned in such a way that these can abut under thesqueezing-out force, in gap-free fashion, against the end face 11 and inthis way form an effective sealing.

The embodiment according to FIGS. 2 and 3 is distinguished in that atthe disk 24, there is disposed a sealing ring 25 which has two resilientsealing lips which are inclined obliquely towards the end face 11 andaway from one another. When these sealing lips are pressed against theend face 11 under the action of the plunger pressure, they are deformedin the manner as shown in FIG. 3. In this case, the space enclosed bythe lips 26 and the end face 11 is to a large extent emptied. When theplunger pressure ends, the lips form a suction cup which is held firmlyat the end face 11 and which prevents the lifting-off of the lips 26from the end face 11 and thus the movement of breathing and the lack ofsealing which would otherwise be associated therewith.

In FIG. 4, it is assumed that the floor 4 of the cartridge is fixedlyconnected to its wall 3 and the tubular bag 1 is inserted into thecartridge from the side remote from the expulsion side. However, thisdoes not need to be so.

At the rear end of the tubular bag 1, which faces that end 6 of thecartridge which is remote from the floor, there is fitted onto thetubular bag a disk 30, which includes, at the centre, an opening toreceive the closure cord 31 of the bag. Its periphery cooperates infrictional fashion with the inner surface of the cartridge 2. Uponinsertion of the tubular bag into the cartridge, the insertion force istransmitted to the bag via the disk 30. Accordingly, the frictionalforce at the periphery of the disk 30 does not have an effect on theinternal pressure of the bag 1. If the cartridge together with the bagcontained therein is stored outside the expulsion unit and erectedvertically with the rear end downwards, then the frictional force at theperiphery of the disk 30 absorbs the weight of the filled bag 1 andholds it in the existing position.

The periphery of the disk 30 can be provided with devices which, even inthe case of the existence of certain dimensional tolerances of the disk30 and of the cartridge 2, maintain the frictional force within adesired range, for example by means of a friction-increasing elastomerring 32. As shown in FIG. 4, a design can be selected in this case whichdoes indeed set against the rearward movement of the bag a frictionalforce of desired magnitude, but offers only slight resistance to theinsertion of the bag into the cartridge from the rear end of the latter.To this end, the plane 33, in which the line of the contact between theperiphery of the disk 30 acting as braking component and the innersurface of the cartridge 2 lies, is rearwardly offset in relation to themain plane 34 of the disk. In the event of axial movement of the disk,the friction generates at its periphery a bending moment, which, in thecase of movement directed into the cartridge, urges the contact regionradially inwards with reduction of friction and, in the case of thereverse direction of movement, urges it radially outwards with acorresponding increase in friction. In this case, the lip 35 forming thefrictional contact can consist of soft material. It may have therepresented rearward inclination already in the shaped, relaxedcondition; however, it is also possible that the lip lies within themain plane 34 of the disk in the relaxed condition and adopts theinclined position only upon insertion into the cartridge.

The periphery of the disk 30, which periphery abuts against the innerwall of the cartridge 2, does not need to be continuous; rather, it maybe interrupted, so that a plurality of flexible arms is formed, the endsof which abut resiliently against the cartridge wall and are connectedto one another only in the central region.

The axial offset between the contact plane 33 and the main plane 34 ofthe disk 30 or of its arms does not need to be predetermined by itsoriginal form; rather, the part can also be designed to be flat and mayassume the outwardly rearwardly bent form only as a result of resilientdeformation upon insertion into the cartridge. In each case, thediameter of the relaxed disk 30 is greater than the internal diameter ofthe cartridge, so that the disk periphery or the ends of the arms abutagainst the cartridge wall with a certain pretension.

What is claimed is:
 1. Arrangement for squeezing a flowable material outof a tubular bag having an outside diameter and oppositely disposedfirst and second ends, the first end of the tubular bag defining anopening which is surrounded by a shoulder of the tubular bag, thearrangement comprising: a squeezing-out unit having oppositely disposedfirst and second ends and defining a cylindrical space which receivesthe tubular bag, the first end of the unit having an end face disposedopposite the shoulder of the tubular bag, the end face defining adischarge opening which cooperates with the bag opening, the second endof the unit receiving a pressing plunger; and a sealing ring having atleast one sealing component and disk means for connecting the sealingring to the tubular bag in an angularly movable fashion, the disk meanshaving an annular bead facing the tubular bag, the annular bead having adiameter which is substantially less than the outside diameter of thetubular bag, the disk means being adhesively bonded to the first end ofthe tubular bag only within the annular bead, the sealing componentcooperating with the end face surrounding the discharge opening to sealthe discharge opening from the cylindrical space of the unit. 2.Arrangement according to claim 1 wherein the opening of the bag isformed by a gathering of the bag, the gathering penetrating through thesealing ring and lying freely in the discharge opening.
 3. Arrangementaccording to claim 1 wherein the sealing component is yieldable. 4.Arrangement according to claim 1 wherein the sealing component of thesealing ring is formed by at least one annular projection. 5.Arrangement according to claim 1 wherein the external diameter of thesealing ring is slightly smaller than the inside diameter of thecylindrical space to facilitate centering the sealing ring in thesqueezing-out unit.
 6. Arrangement according to claim 1 wherein thesealing ring is provided with at least one retaining part arresting thesealing ring in the sealing position.
 7. Arrangement according to claim6 wherein the retaining part comprises at least one suction holdercooperating with the end face.
 8. Arrangement according to claim 1wherein the second end of the bag comprises a braking component whichfrictionally engages the wall of the cylindrical space at least in adirection which resists removal of the bag from the cylindrical space.9. Arrangement according to claim 8 wherein the braking componentcomprises a disk or a ring disposed intermediate the pressing plungerand the tubular bag by means of which the pressing plunger acts on thetubular bag.
 10. Arrangement according to claim 8 wherein the brakingcomponent has a diameter which is greater than the internal diameter ofthe cylindrical space.
 11. Arrangement according to claim 8 wherein afirst portion of the braking component engages the wall of thecylindrical space along a circular line of contact, defining a firstplane, and a second portion of the braking component abuts against thetubular bag, defining a second plane, wherein the first plane is offsetfrom the second plane in a direction away from the tubular bag. 12.Arrangement according to claim 8 wherein the braking component has aninterrupted periphery.